Adhesive sheet for dicing glass substrate

ABSTRACT

An adhesive sheet for dicing glass substrate includes a base film and an adhesive layer arranged on the base film. The base film has a thickness of 130 μm or more and a tensile modulus of 1 GPa or more, and the adhesive layer has a thickness of 9 μm or less. The adhesive sheet can give cut pieces excellent in shape and hardly causes cut pieces to be chipped or to scatter chips.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 10/452,893,filed Jun. 2, 2003, which claims priority to Japanese Patent ApplicationNo. 2002-168820, filed Jun. 10, 2002, and the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an adhesive sheet for dicing glasssubstrate and a method of dicing glass substrate. This invention alsorelates to a cut piece of glass substrate, which is obtained by thismethod. The adhesive sheet for dicing glass substrate can be utilized invarious industrial fields and is particularly useful as e.g. a glasssubstrate-fixing sheet used for sticking and fixing a glass substrateprovided with semiconductor circuits or a glass substrate used inoptical communication etc. in order to cut the glass substrate intosmall pieces.

2. Description of the Related Art

Semiconductor products or optical articles made of glass, quartz, rockcrystal, sapphire or lens are produced by cutting and separating(dicing) a glass substrate having formed various circuits or subjectedto surface treatment etc., to form small pieces serving as individualelements or parts. In this production process, the glass substratehaving an adhesive sheet stuck thereon is subjected to a dicing step, awashing step, a drying step and a pick-up step respectively and then toa subsequent step. The adhesive sheet used in the dicing to pick-upsteps of the glass substrate is desired to exhibit sufficient adhesionto cut pieces in the dicing to drying steps and to exhibit adhesion inthe pick-up step to such an extent that its adhesive does not adhere tothe cut pieces.

As the adhesive sheet for dicing glass substrate, a dicing adhesivesheet applied to semiconductor wafers has been used. The thickness ofsuch a dicing adhesive sheet is usually about 70 to 120 μm.

The glass substrate is thicker than a semiconductor wafer and is thusdiced by using a blade having a thickness of about 150 to 300 μm inorder to conduct stable dicing. Due to a round top of the dicing blade,however, a cut piece from a conventional dicing adhesive sheet has abroader width in a lower section, to have an irregular shape like skirt.

Further, the glass substrate is very brittle and easily broken.Accordingly, when the adhesive sheet for fixing the glass substrate issignificantly deformed by pressure from the dicing blade, the glasssubstrate cannot endure the deformation and is thus broken to causechipping or to scatter chips, causing a problem in qualities of cutpieces.

An object of the present invention is to provide an adhesive sheet fordicing glass substrate, which can give cut pieces excellent in shape andhardly causes cut pieces to be chipped or to scatter chips. Anotherobject of this invention is to provide a method of dicing glasssubstrate by using this adhesive sheet. A still other object of thisinvention is to provide a cut piece of glass substrate, which isobtained by this method.

SUMMARY OF THE INVENTION

As a result of extensive study to solve the problem described above, thepresent inventors found that these objects can be achieved by using thefollowing adhesive sheet for dicing glass substrate.

That is, this invention relates to an adhesive sheet for dicing glasssubstrate comprising a base film and an adhesive layer arranged on thebase film, wherein the base film has a thickness of 130 μm or more and atensile modulus of 1 GPa or more, and the adhesive layer has a thicknessof 9 μm or less.

In the adhesive sheet described above, the thickness of the base film is130 μm or more, thus preventing an irregular shape of cut piecesobtained by dicing of glass substrate, to give cut pieces excellent inshape. The thickness of the base film is usually from 130 μm to 300 μm.The thickness of the base film is preferably 150 to 300 μm, morepreferably 150 to 250 μm, still more preferably 150 to 225 μm.

The base film makes use of a rigid material having a tensile modulus of1 GPa or more. The tensile modulus of the base film is preferably 1 to 4GPa, more preferably 1.5 to 4 GPa. As the base film having such tensilemodulus, a polyester film is preferably used. A base film made of a softmaterial such as polyethylene or polyvinyl chloride permits significantdeformation of the adhesive sheet, while a base film of a relativelyrigid material having a thickness of 130 μm or more and a tensilemodulus of 1 GPa or more can prevent deformation of the adhesive sheet.In addition, the thickness of the adhesive layer is 9 μm or less, thusreducing the deformation of the adhesive sheet by pressure from a dicingblade and hardly causing cut pieces to be chipped or to scatter chips.The thickness of the adhesive layer is preferably 4 to 9 μm, morepreferably 4 to 7 μm.

JP-A 2000-281990 discloses an adhesive sheet for dicing containing asubstrate having a thickness of 70 to 300 μm. However, the adhesivesheet is used as an adhesive sheet for package substrate having asignificantly uneven surface, thus requiring an adhesive layer of 10 to50 μm in thickness. The adhesive sheet having such thick adhesive layercannot prevent cut pieces from being chipped or scattering chips.

In the adhesive sheet for dicing glass substrate, its adhesive layer ispreferably a radiation-curing adhesive layer. The radiation-curingadhesive layer exhibits sufficient initial adhesion to a glass substrateto fix the substrate to the adhesive sheet in the dicing step. In thepick-up step, the radiation-curing adhesive layer can reduce theadhesion irradiated with UV rays, to make it easy to pick cut pieces upfrom the adhesive sheet. The UV-curing adhesive layer is particularlypreferably used for a brittle and easily broken glass substrate.

As the UV-curing adhesive sheet, for example a UV-curing adhesive sheetcoated with an adhesive comprising a low-molecular compound having atleast 2 photo-polymerizable carbon-carbon double bonds in its moleculecapable of forming a three-dimensional network upon irradiation of thesurface of a base substrate with UV rays has been proposed in JP-A60-196956 and JP-A 60-223139.

This invention also relates to a method of dicing glass substratecomprising steps of: sticking the above adhesive sheet on a glasssubstrate, and dicing the glass substrate. The resulting cut pieces(elements etc.) of the glass substrate are excellent in shape and areprevented from being chipped and scattering chips. Accordingly, thepresent method can contribute significantly to improving the productionyield of elements in a user line.

The method of dicing glass substrate can also be applied preferably tocutting of a glass substrate by dicing into pieces of 3 mm×3 mm or lessin size. Generally, when the size of cut pieces is 3 mm×3 mm or less,the cut pieces have an irregular shape or easily undergo chipping orscatter chips, but the adhesive sheet of this invention can provide cutpieces without such problems. Depending on use, the size of the cutpieces can be suitably determined without particular limitation. Becausethe cut pieces are usually square, their size is expressed as describedabove, but the shape of the cut pieces can also be suitably determineddepending on use, without particular limitation.

In the method of dicing glass substrate, the glass substrate is dicedpreferably after being left for at least 24 hours after sticking theadhesive sheet thereon. When the size of cut pieces is small, the dicingof the glass substrate immediately after sticking the adhesive sheetthereon tends to cause scattering of chips in a large amount, but whenthe glass substrate is diced after being left for at least 24 hoursafter sticking the adhesive sheet thereon until the adhesive comes tohave sufficient adhesion, scattering of chips can be prevented even ifthe glass substrate is cut into pieces of 1 mm×1 mm or less in size.Depending on the size of cut pieces, the time for which the glasssubstrate is left can be suitably determined without particularlimitation. For example, when the size of the cut pieces is 3 mm×3 mm,the glass substrate is left for 12 hours or more, and when the size ofthe cut pieces is 5 mm×5 mm, the glass substrate is left for 0.5 hour ormore, whereby chip scattering can be prevented.

In the method of dicing glass substrate, the adhesive sheet is stuck onthe glass substrate preferably under heating at a temperature of 40° C.or more. When the size of cut pieces is small, chip scattering tends tooccur significantly, but when the glass substrate during sticking theadhesive sheet thereon is at 40° C. or more, adhesion is rapidlyexhibited to prevent chip scattering in the subsequent chipping stepeven if the glass substrate are cut into small pieces of 1 mm×1 mm insize. The temperature of the glass substrate during sticking theadhesive sheet is preferably in the range of 40 to 80° C., morepreferably 40 to 60° C. When the adhesive sheet stuck at the abovetemperature on the glass substrate is left, the adhesive sheet is leftusually at ordinary temperatures.

Further, this invention relates to a cut piece of glass substrate, whichis obtained by the method of dicing glass substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example drawing showing sectional view of the adhesivesheet for dicing glass substrate.

FIG. 2 is an example drawing showing backside chipping.

FIG. 3 is an example drawing showing irregular shape of section of cutpiece.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the adhesive sheet for dicing glass substrate according tothe present invention is described in more detail by reference to thedrawings. FIG. 1 shows a section of the adhesive sheet for dicing glasssubstrate, comprising an adhesive layer 2 arranged on a base film 1. Theadhesive layer 2 can be provided with a separator 3.

The base film makes use of a material having a tensile modulus of 1 GPaor more. The base film made of such a material includes, for example,polyester film, polyphenylene sulfide film etc. The polyester includespolyethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate etc. Among these polyesters, polyethylene terephthalate ispreferable. These base films may be non-stretched or may be subjected ifnecessary to uniaxial or biaxial stretching. The surface of the basefilm can be subjected if necessary to ordinary physical or chemicaltreatment such as treatment with a releasing agent, matt treatment,corona discharge treatment, primer treatment, and crosslinkingtreatment. The thickness of the base film is 130 μm or more as describedabove.

The adhesive that can be used in formation of the adhesive layer may befor example a generally used pressure-sensitive adhesive, and suitableadhesives such as acrylic adhesive, saturated polyester-based adhesiveand rubber-based adhesive can be used. In particular, the acrylicadhesive based on an acrylic polymer is used preferably because of itsadhesion to the base film and its easy molecular design.

The acrylic polymer include acrylic polymers made from one or more alkyl(meth) acrylates (for example, C₁₋₃₀ alkyl, particularly C₄₋₁₈ linear orbranched alkyl esters such as methyl ester, ethyl ester, propyl ester,isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butylester, pentyl ester, isopentyl ester, hexyl ester, heptyl ester, octylester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester,isodecyl ester, undecyl ester, dodecyl ester, tridecyl ester, tetradecylester, hexadecyl ester, octadecyl ester and eicosyl ester) andcycloalkyl (meth) acrylates (for example, cyclopentyl ester, cyclohexylester etc.) as monomer components. As main monomers, alkyl acrylatesgiving homopolymers having a glass transition point of −50° C. or lessare usually used. The (meth) acrylates refer to acrylates and/ormethacrylates, and the term “(meth)” in this invention is used in thismeaning.

For the purpose of improving cohesive force, heat resistance etc., theacrylic polymer may, if necessary, contain monomers corresponding toother monomer components copolymerizable with the alkyl (meth) acrylatesor cycloalkyl esters. Such monomer components include, for example,carboxyl group-containing monomers such as acrylic acid, methacrylicacid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate,itaconic acid, maleic acid, fumaric acid and crotonic acid; acidanhydride monomers such as maleic anhydride and itaconic anhydride;hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth)acrylate and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate;sulfonate group-containing monomers such as styrenesulfonic acid,allylsulfonic acid, 2-(meth) acrylamide-2-methylpropanesulfonic acid,(meth) acrylamide propanesulfonic acid, sulfopropyl (meth) acrylate and(meth) acryloyloxy naphthalenesulfonic acid; phosphate group-containingmonomers such as 2-hydroxyethylacryloyl phosphate; and glycidyl (meth)acrylate, (meth) acrylamide, N-hydroxymethylamide (meth) acrylate,alkylamioalkyl (meth) acrylates such as dimethylaminoethyl methacrylateand t-butylaminoethyl methacrylate, vinyl acetate, styrene andacrylonitrile. These copolymerizable monomer components can be usedalone or in combination thereof. The amount of these copolymerizablemonomers used is preferably 40% by weight or less based on the wholemonomer components.

For crosslinking, the acrylic polymer can contain copolymerizablemonomer components such as multifunctional monomers are necessary. Themultifunctional monomers include, for example, hexanedioldi(meth)acrylate, (poly)ethylene glycol di(meth)acrylate,(poly)propylene glycol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylol propanetri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritolhexa(meth)acrylate, epoxy(meth)acrylate, polyester (meth)acrylate,urethane (meth)acrylate etc. These multifunctional monomers can also beused alone or in combination thereof. From the viewpoint of adhesioncharacteristics etc., the amount of the multifunctional monomers used ispreferably 30% by weight or less based on the whole monomer components.

The acrylic polymer is obtained by polymerizing a single monomer or amixture of two or more monomers. Polymerization can be carried out inany systems such as solution polymerization, emulsion polymerization,bulk polymerization and suspension polymerization. From the viewpoint ofpreventing pollution of semiconductor wafers etc., the content oflow-molecular components in the adhesive layer is preferably lower asdescribed above. From this viewpoint, the number-average molecularweight of the acrylic polymer is preferably 300,000 or more, morepreferably 400,000 to 3,000,000.

The saturated polyester includes, for example, saturated polyesters, acondensation product of polyvalent alcohols with polyvalent carboxylicacids. The polyvalent alcohols include glycols such as ethylene glycol,propylene glycol and 1,4-butanediol. The polyvalent carboxylic acidsinclude aromatic dicarboxylic acids such as terephthalic acid andisophthalic acid, and fatty dicarboxylic acids such as adipic acid andsebacic acid. The saturated polyester is preferably a saturatedcopolyester using two or more polyvalent carboxylic acids, for examplean aromatic dicarboxylic acid and a fatty dicarboxylic acid.

An external crosslinking agent can also be added to the adhesive. Themethod of crosslinking is exemplarily a method of adding apolyisocyanate compound, an epoxy compound, an aziridine compound, amelamine-based crosslinking agent, urea resin, an acid anhydride,polyamine, a carboxyl group-containing polymer or the like thereto andreacting the mixture. When the external crosslinking agent is used, itsamount is determined suitably depending on balance with the base polymerto be crosslinked or on the intended use of the adhesive. Generally, thecrosslinking agent is compounded in an amount of 5 parts by weight orless based on 100 parts by weight of the base polymer.

The adhesive may make use of a wide variety of conventionally knownadditives such as a tackifier, a plasticizer, a filler, an aginginhibitor and a coloring agent if necessary in addition to thecomponents described above.

The adhesive layer can be prepared so as to be releasable by formingthis layer from a radiation-curing adhesive or a thermally foamingadhesive. When the thermally foaming adhesive is used, two or moreadhesive layers are formed, and the adhesive layer at the side of thebase film is preferably produced from the thermally foaming adhesive. Inthis case, the adhesive layer as the surface layer can be produced froma radiation-curing adhesive.

The radiation-curing adhesive is not limited insofar as it hasradiation-curing functional groups such as carbon-carbon double bondsand exhibits adhesion. The radiation-curing adhesive is desirably theone lowering adhesion upon irradiation with radiations, particularly UVrays.

The radiation-curing adhesive includes, for example radiation-curingadhesives of addition type comprising radiation-curing componentsincorporated into general pressure-sensitive adhesives such as theacrylic adhesive, saturated polyester-based adhesive and rubber-basedadhesive described above. The radiation-curing components includemonomers, oligomers and polymers having carbon-carbon double bonds inthe molecule and curable by radiation polymerization.

The radiation-curing monomer components incorporated include, forexample, urethane (meth)acrylate; esters of (meth)acrylic acid withpolyvalent alcohol, for example trimethylol propane tri(meth)acrylate,tetramethylol methane tetra(meth)acrylate, pentaerythritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritolhexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, tetraethyleneglycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate and neopentylglycol di(meth)acrylate; and cyanurate compounds or isocyanuratecompounds such as 2-propenyl di-3-butenyl cyanurate, 2-hydroxyethylbis(2-acryloxyethyl) isocyanurate, tris(2-acryloxyethyl) isocyanurateand tris(2-methacryloxyethyl) isocyanurate. The radiation-curingoligomer components include various oligomers based on urethane,polyether, polyester, polycarbonate or polybutadiene, and the molecularweight thereof is preferably in the range of 100 to 30,000. Depending onthe type of the adhesive layer, the amount of the radiation-curingmonomer components and oligomer components blended can be suitablydetermined such that the adhesion of the adhesive layer can be reduced.Generally, their amount is for example not higher than 500 parts byweight, preferably not higher than 150 parts by weight, based on 100parts by weight of the base polymer such as the acrylic polymerconstituting the adhesive.

The radiation-curing adhesive includes not only the radiation-curingadhesives of addition type described above, but also inherentradiation-curing adhesives using a base polymer, having carbon-carbondouble bonds in side or main chains or terminals of main chains of thepolymer. The inherent radiation-curing adhesive is preferably usedbecause it does not require low-molecular oligomer components etc. ordoes not contain a large amount of such components, and thus an adhesivelayer of stabilized layer structure can be formed without migration withtime of oligomer components etc. in the adhesive.

The base polymer having carbon-carbon double bonds is not particularlylimited insofar as it has carbon-carbon double bonds and exhibitsadhesion. The base polymer is preferably the one having an acrylicpolymer as the fundamental skeleton. The fundamental skeleton of theacrylic polymer includes the acrylic polymer exemplified above.

The method of introducing carbon-carbon double bonds into the acrylicpolymer is not particularly limited, and various methods can be used,but introduction of carbon-carbon double bonds into side chains of thepolymer makes molecular design easy. For example, a monomer having afunctional group is copolymerized as a component of the acrylic polymer,followed by subjecting the resulting copolymer to condensation oraddition reaction with a compound having a carbon-carbon double bond anda functional group capable of reacting with the above functional groupwhile maintaining the radiation-curing properties of the carbon-carbondouble bond during the reaction.

The combination of such functional groups includes, for example,combinations of carboxy group and epoxy group, carboxy group andaziridyl group, or hydroxyl group and isocyanate group. Among thesecombinations of functional groups, a combination of hydroxyl group andisocyanate group is preferable because the reaction can be easilymonitored. The functional groups may present in the acrylic polymer orthe above compound insofar as the acrylic polymer having carbon-carbondouble bonds can be produced by the combination of functional groups,but it is preferable that in the preferable combination described above,the acrylic polymer has a hydroxyl group while the above compound has anisocyanate group. In this case, the isocyanate compound having acarbon-carbon double bond includes, for example, methacryloylisocyanate, 2-methacryloyloxyethyl isocyanate,m-isopropenyl-α,α-dimethylbenzyl diisocyanate etc. The acrylic polymermakes use of a copolymer of the above-exemplified hydroxylgroup-containing monomer and an ether-based compound such as2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, or diethyleneglycol monovinyl ether.

In the inherent radiation-curing adhesive, the base polymer havingcarbon-carbon double bonds, particularly the acrylic polymer, can beused alone, but the radiation-curing monomer components and oligomercomponents can also be compounded therein to such an extent as not todeteriorate the characteristics. The amount of the radiation-curingoligomer components etc. is usually 30% by weight or less, preferably10% by weight or less, based on 100 parts by weight of the base polymer.

For curing with UV rays etc., a photopolymerization initiator iscontained in the radiation-curing adhesive. The photopolymerizationinitiator may be any compound cleaved to form radicals upon irradiationwith UV rays of suitable wavelength capable of causing thepolymerization reaction. The photopolymerization initiator includes, forexample, benzoin alkyl ethers such as benzoin methyl ether, benzoinisopropyl ether and benzoin isobutyl ether; aromatic ketones such asbenzyl, benzoin, benzophenone and α-hydroxy cyclohexyl phenyl ketone;aromatic ketals such as benzyl dimethyl ketal; polyvinyl benzophenone;and thioxanthones such as chlorothioxanthone, dodecyl thioxanthone,dimethyl thioxanthone and diethyl thioxanthone. The amount of thephotopolymerization initiator is for example 1 to 10 parts by weight,preferably 3 to 5 parts by weight, based on 100 parts by weight of thebase polymer such as the acrylic polymer constituting the adhesive.

On one hand, the thermally foaming adhesive comprises thermallyexpandable fine particles incorporated into the generalpressure-sensitive adhesive described above. The thermally foamingadhesive facilitates release by reducing the adhesion area by foamingthe thermally expandable fine particles upon heating, and the averageparticle diameter of the thermally expandable fine particles ispreferably 1 to 25 μm. The average particle diameter is more preferably5 to 15 μm, still more preferably about 10 μm. The thermally expandablefine particles are not particularly limited insofar as they can expandunder heating. For example, thermally expandable microcapsules producedby in-situ polymerization by encapsulating suitable low-boilingcomponents forming gases such as butane, propane or pentane in copolymerwalls of vinyl chloride, acrylonitrile etc. The thermally expandablemicrocapsules have an advantage that they are excellent in an ability tobe dispersed in and mixed with the adhesive. Commercial products of thethermally expandable microcapsules include, for example, Microsphere™manufactured by Matsumoto Yushi Co., Ltd.

Depending on the type of the adhesive layer, the amount of the thermallyexpandable fine particles, exemplified the thermally expandablemicrocapsules, incorporated into the adhesive can be suitably determinedsuch that the adhesion of the adhesive can be reduced, and this amountis generally 1 to 100 parts by weight, preferably 5 to 50 parts byweight, more preferably 10 to 40 parts by weight, based on 100 parts byweight of the base polymer.

The adhesive sheet of the present invention can be produced for exampleby forming an adhesive layer on the base film. The method of forming theadhesive layer is not particularly limited, and use can be made of, forexample, a method of forming the adhesive layer by applying it directlyonto the base film or a method forming the adhesive layer by separatelyforming it on a separator and then sticking the adhesive layer on thebase film. The thickness of the adhesive layer is 7 μm or less is morepreferable. From the viewpoint of reducing chipping, an adhesive layerhaving a storage modulus (23° C.) of 3×10¹ to 1×10⁵ N/cm² at 0 to 10° C.is preferably used.

A base film constituting the separator is not particularly limitedinsofar as it is a film (including a sheet) capable of protecting theadhesive layer. Examples thereof include plastic films such as polyetherether ketone, polyether imide, polyallylate, polyethylene naphthalate,polyethylene film, polypropylene film, polybutene film, polybutadienefilm, polymethylpentene film, polyvinyl chloride film, vinyl chloridecopolymer film, polyethylene terephthalate film, polybutyleneterephthalate film, polyurethane film, ethylene-vinyl acetate copolymerfilm, ionomer resin film, ethylene-(meth)acrylic acid copolymer film,ethylene-(meth)acrylate copolymer film, polystyrene film andpolycarbonate film.

A thickness of the film is usually 5 to 200 μm, preferably 25 to 100 μm,more preferably 38 to 60 μm. The surface of the film on which theadhesive is stuck may be treated with a releasing agent based onsilicone (including UV curing agent), fluorine, or a long alkyl or fattyamide, or with silica.

The adhesive sheet of this invention is stored usually in a rolled stateand unrolled if necessary for use in the dicing step.

EXAMPLES

Hereinafter, the present invention is described in more detail byreference to the Examples, but this invention is not limited by theExamples. The tensile modulus of the base film is initial tensilemodulus determined from an S—S curve obtained by pulling it at a rate of300 mm/min. at 23° C., with a film width of 10 mm and a distance betweenchucks of 10 mm.

Example 1

A composition comprising of 70 parts by weight of methyl acrylate, 30parts by weight of butyl acrylate and 5 parts by weight of acrylic acidwas copolymerized in ethyl acetate to obtain a solution having a solidscontent of 25% by weight, containing an acrylic copolymer having anumber-average molecular weight of 800,000. To the solution was added 60parts by weight of dipentaerythritol hexaacrylate (Karayad DPHA™,manufactured by Nippon Kayaku Co., Ltd.), 5 parts by weight of a radicalpolymerization initiator (Irgacure 651™, manufactured by CibaSpecialties Chemicals) and 5 parts by a polyisocyanate compound(Coronate L™, manufactured by Nippon Polyurethane), whereby an acrylicUV-curing adhesive solution was prepared.

As the base film, a polyester film of 150 μm in thickness (tensilemodulus 1.5 GPa), one side of which had been treated with corona, wasused. The corona-treated side of this base film was coated with theabove adhesive solution and dried under heating, to form a UV-curingadhesive layer of 4 μm in thickness thereon. Then, a separator was stuckon the surface of the adhesive layer to produce a UV-curing adhesivesheet. As the separator, a polyester film of 38 μm in thickness (LuminarS-10 #50™, manufactured by Toray), having an adhesive layer-stickingsurface subjected to treatment with a releasing agent, was used.

Example 2

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a thickness of the adhesive layer was 5 μm.

Example 3

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a thickness of the adhesive layer was 7 μm.

Example 4

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a polyester film of 188 μm in thickness was used as thebase film, and a thickness of the adhesive layer was 5 μm.

Example 5

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a polyester film of 225 μm in thickness was used as thebase film, and a thickness of the adhesive layer was 5 μm.

Comparative Example 1

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a thickness of the adhesive layer was 10 μm.

Comparative Example 2

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a thickness of the adhesive layer was 20 μm.

Comparative Example 3

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a polyester film of 125 μm in thickness was used as thebase film.

Comparative Example 4

A UV-curing adhesive sheet was obtained in the same manner as in Example1 except that a polyvinyl chloride film of 185 μm in thickness (tensilemodulus, 0.2 GPa) was used as the base film, and a thickness of theadhesive layer was 5 μm.

The thickness of each of the base films and adhesive layers obtained inthe Examples and Comparative Examples is shown in Table 1. TABLE 1Thickness (μm) Base film Adhesive layer Example 1 150 4 Example 2 150 5Example 3 150 7 Example 4 188 5 Example 5 225 5 Comparative Example 1150 10 Comparative Example 2 150 20 Comparative Example 3 125 5Comparative Example 4 185 5

Evaluation Tests

The UV-curing adhesive sheets obtained in the Examples and ComparativeExamples were evaluated in the following manner.

(1) Dicing Test

A soda glass (a glass substrate) of 1 mm in thickness was left for 10minutes on a substrate at a predetermined temperature (23° C., 40° C.,60° C.) such that the temperature of the glass substrate was madeidentical with the predetermined temperature of the substrate. Then, theadhesive sheet was stuck on the glass substrate, then left at ordinarytemperatures for a predetermined time (0.5 hour, 3 hours, 12 hours, 24hours) and diced under the following conditions.

Cut speed: 2.5 mm/s

Number of revolutions of spindle: 20,000 rpm

Blade: G1A851SD400R13B01 blade having a thickness of 210 μm,manufactured by DISCO

Cutting height: 50 μm

Dicing was conducted for cut piece sizes of 1 mm×1 mm, 3 mm×3 mm and 5mm×5 mm, respectively. After dicing was finished, the state of chipscattering including surrounding chips was evaluated under the followingcriteria. The results are shown in Tables 2, 3 and 4 for the respectivesizes of the cut pieces.

⊚: No scattering of chips in the surrounding region and in the product.

∘: Slight scattering of chips in the surrounding region with noscattering of chips in the product.

X: Much scattering of chips in the surrounding region and scattering ofchips in the product. TABLE 2 Scattering of chips during sizing/dicingsize: 1 mm × 1 mm Temperature (° C.) of the Time (hours) substrateelapsed after Example Example Example Example Example ComparativeComparative Comparative Comparative during sticking sticking 1 2 3 4 5Example 1 Example 2 Example 3 Example 4 23 0.5 X X X X X ⊚ ⊚ X X 3 X X ◯X X — — X X 12 X ◯ ◯ ◯ ◯ — — X ◯ 24 ◯ ◯ ⊚ ◯ ◯ — — ◯ ◯ 40 0.5 ◯ ◯ ⊚ ◯ ◯ —— ◯ ◯ 60 0.5 ⊚ ⊚ ⊚ ⊚ ⊚ — — ⊚ ⊚

TABLE 3 Scattering of chips during sizing/dicing size: 3 mm × 3 mmTemperature (° C.) of the Time (hours) substrate elapsed after ExampleExample Example Example Example Comparative Comparative ComparativeComparative during sticking sticking 1 2 3 4 5 Example 1 Example 2Example 3 Example 4 23 0.5 X X ◯ X X ⊚ ⊚ X X 3 X ◯ ◯ ◯ ◯ — — X ◯ 12 ◯ ◯⊚ ◯ ◯ — — ◯ ◯ 24 ⊚ ⊚ ⊚ ⊚ ⊚ — — ⊚ ⊚ 40 0.5 ⊚ ⊚ ⊚ ⊚ ⊚ — — ⊚ ⊚ 60 0.5 ⊚ ⊚ ⊚⊚ ⊚ — — ⊚ ⊚

TABLE 4 Scattering of chips during sizing/dicing size: 5 mm × 5 mmTemperature (° C.) of the Time (hours) substrate elapsed after ExampleExample Example Example Example Comparative Comparative Comparativeduring sticking sticking 1 2 3 4 5 Example 1 Example 2 Example 3 23 0.5◯ ◯ ◯ ◯ ◯ ⊚ ⊚ ◯ 3 ◯ ◯ ◯ ◯ ◯ — — ◯ 12 ◯ ◯ ⊚ ◯ ◯ — — ◯ 24 ⊚ ⊚ ⊚ ⊚ ⊚ — — ⊚40 0.5 ⊚ ⊚ ⊚ ⊚ ⊚ — — ⊚ 60 0.5 ⊚ ⊚ ⊚ ⊚ ⊚ — — ⊚

(2) Backside Chipping

After the dicing (temperature of the substrate during sticking, 60° C.;the time elapsed after sticking, 0.5 hour; the size of cut pieces, 3mm×3 mm), the cut pieces were irradiated with UV rays at 35 mW/cm²·s for13 seconds, and the cut glass substrate(G) was released from theadhesive sheet. The first, the second, the third and the fourth cut linewere represented by L1, L2, L3 and L4. Chipping in the fourth cutline(L4) on the back of the cut glass substrate(G) was observed under amicroscope. As shown in FIG. 2, the maximum chipping (W: μm) wasmeasured for each of the chips, and the average value of 20 chips wasexpressed as the amount of chips. The results are shown in Table 5.

(3) Irregular Shape

After the dicing (temperature of the substrate during sticking, 60° C.;the time elapsed after sticking, 0.5 hour; the size of cut pieces, 3mm×3 mm), a section of each cut piece was observed under a microscopeand evaluated under the following criteria. In Comparative Example 5,all chips had cracking. The results are shown in Table 5. TABLE 5Chipping (μm) Irregular shape Example 1 18 ∘ Example 2 21 ∘ Example 3 28∘ Example 4 24 ∘ Example 5 22 ∘ Comparative Example 1 40 ∘ ComparativeExample 2 63 ∘ Comparative Example 3 19 x Comparative Example 4 27 x∘: The section was straight.x: The section had an irregular shape as shown in FIG. 3.

1. An adhesive sheet for dicing a glass substrate, comprising: a singlebase film having a thickness of 130 μm or more and a tensile modulus of1-4 GPa; and an adhesive layer formed on the base film at a thickness of9 μm or less.
 2. The adhesive sheet for dicing a glass substrateaccording to claim 1, wherein the base film is a polyester film.
 3. Theadhesive sheet for dicing a glass substrate according to claim 1,wherein the adhesive layer is a radiation-curing adhesive layer.
 4. Theadhesive sheet for dicing a glass substrate according to claim 1,wherein the surface of the base film on which the adhesive film isformed is corona-treated.
 5. A cut piece of a glass substratecomprising: a glass substrate; and the adhesive sheet of claim 1attached to the glass substrate, said glass substrate with the adhesivesheet being diced.
 6. The cut piece according to claim 5, wherein thebase film of the adhesive sheet is a polyester film.
 7. The cut pieceaccording to claim 5, wherein the adhesive layer of the adhesive sheetis a radiation-curing adhesive layer.
 8. The cut piece according toclaim 5, wherein the glass substrate is cut by dicing into pieces of 3mm×3 mm or less in size.